From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 14 Dec 2005 11:08:41 +0100 From: Pavel Machek Subject: Re: [RFC][PATCH 0/6] Critical Page Pool Message-ID: <20051214100841.GA18381@elf.ucw.cz> References: <439FCECA.3060909@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <439FCECA.3060909@us.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Matthew Dobson Cc: linux-kernel@vger.kernel.org, andrea@suse.de, Sridhar Samudrala , Andrew Morton , Linux Memory Management List-ID: Hi! > The overall purpose of this patch series is to all a system administrator > to reserve a number of pages in a 'critical pool' that is set aside for > situations when the system is 'in emergency'. It is up to the individual > administrator to determine when his/her system is 'in emergency'. This is > not meant to (necessarily) anticipate OOM situations, though that is > certainly one possible use. The purpose this was originally designed for > is to allow the networking code to keep functioning despite the sytem > losing its (potentially networked) swap device, and thus temporarily > putting the system under exreme memory pressure. I don't see how this can ever work. How can _userspace_ know about what allocations are critical to the kernel?! And as you noticed, it does not work for your original usage case, because reserved memory pool would have to be "sum of all network interface bandwidths * ammount of time expected to survive without network" which is way too much. If you want few emergency pages for some strange hack you are doing (swapping over network?), just put swap into ramdisk and swapon() it when you are in emergency, or use memory hotplug and plug few more gigabytes into your machine. But don't go introducing infrastructure that _can't_ be used right. Pavel -- Thanks, Sharp! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org